1. Field of the Invention
Aspects of the present invention relate to asymmetric arylamine derivatives for an organic electroluminescent (which will be occasionally referred to as “EL”, hereinafter) element, a manufacturing method of the same, an organic thin layer material for an organic EL element including the asymmetric arylamine derivatives, and an organic EL element employing the same.
2. Related Art
In line with the recent trend toward large-sized display devices, demand for flat display devices occupying a reduced space is gradually increasing. Accordingly, lightness and an increased viewing angle have become more important. In this regard, an organic electroluminescent (EL) element, which is a novel flat display device, having advantages including lightness, wide viewing angle, and a high-speed response, utilizing a spontaneous light emitting phenomenon, has been attracting attention.
An organic electroluminescence device is a spontaneous light emitting device which utilizes the principle that a fluorescent substance emits light by energy of recombination of holes injected from an anode and electrons injected from a cathode when an electric field is applied. Since an organic EL device of the laminate type driven under a low electric voltage was reported by C. W. Tang et al. of Eastman Kodak Company (C. W. Tang and S. A. VanSlyke, Applied Physics Letters, Volume 51, Pages 913, 1987), many studies have been conducted on organic EL devices using organic materials as the constituting materials.
Lifetime of the organic EL element is most affected by a blue emitting material, and many attempts at improvement of lifetime have conventionally been made by improving the blue emitting material.
Among the conventional attempts, highly efficient organic EL elements have mainly been developed, which use a distyryl compound as an organic light-emitting material and additionally use styrylamine, as disclosed in WO/1994/06175. Korean Patent Publication No. KR2002-0070333 discloses a blue light emitting compound having a diphenyl anthracene structure in its skeleton and an organic EL element using the same. However, the emission efficiency and luminance of the disclosed organic EL element using the blue light emitting compound are always insufficient. In addition, U.S. Pat. No. 6,852,429, Korean Patent Publication No. 2005-0107809 and 2006-0006760 disclose an organic light emitting device using a substituted pyrene based compound, which has, however, reduced blue color purity.
Techniques for realizing a high-quality deep-blue color are disclosed, in which a phenylanthracene derivative (Japanese Patent Publication No. 1996-012600), of using a material having naphthyl groups at 9 and 10 positions of anthracene (Japanese Patent Publication No. 1999-3782), a device material having fluoranthene groups at 9 and 10 positions of anthracene (Japanese Patent Publication No. 2001-257074), or the like, are used as host materials for light emission. Although many studies of anthracene derivatives used as light emitting materials have been conducted, there remain problems that lifetime is insufficient and it is not easy to form a thin film with uniformity. Thus, excellent film forming efficiency cannot be achieved, heat resistance may be poor, and intermolecular aggregation may occur during deposition due to a planar structure. Particularly, the existing methods are not advantageous in that high efficiency, high-quality blue emission and long lifetime cannot be easily achieved.